Strontium (Sr) – Occurrence, Extraction, Properties and Applications of Strontium

Background

While it was recognized by Adair Crawford in 1790, it was not until 1808 when Davy isolated it by electrolysis.

Occurrence

Strontium is usually found in the minerals Celestite (SrSO₄) and strontianite (SrCO₃).

Extraction

Strontium can be prepared by electrolysis of the fused chloride mixed with potassium chloride

Alternatively it can be produced by reducing strontium oxide with aluminium at a temperature high enough to distil off the strontium.

Key Properties

· Strontium is softer than calcium and decomposes in water more vigorously

· It does not absorb nitrogen below 380°C

· It should be stored under kerosene to avoid oxidation

· Freshly cut surfaces of strontium are silvery in appearance, but oxidise rapidly and turn yellowish

· Fine strontium powder will spontaneously ignite in air

Key Applications

· In general, strontium has applications similar to barium and calcium.

· The isotope Sr⁹⁰ has a half life of 28 years and is one of the best high energy beta emitters known and is used in systems for nuclear auxiliary power (SNAP) devices. Such devices have potential use in space vehicles, remote weather stations, navigational buoys etc

· Volatile strontium salts produce a bright crimson flame and are used in pyrotechnics.

· Strontium titanate has an extremely high refractive index and an optical dispersion greater then diamond. This has lead to its use in gemstones, although it has been found to be very soft.